Permanent magnet type synchronous motors, in which permanent magnets are embedded in rotors (hereinafter referred to as “PM motors”), are well known as electric motors used in electric vehicles and the like. Further, methods of reducing eddy current loss by dividing the magnets to be embedded are well known as methods of improving efficiency of the PM motors. According to WO2001/095460, for example, magnet pieces that are divided into a plurality of pieces are adhered to each other to form one long plate-shaped magnet, and this long plate-shaped magnet is inserted into a magnet insertion hole in a rotor core.
According to the above-described literature, the magnet pieces are adhered to each other by aligning the magnet pieces in an outer frame that is formed by organic resin, and applying pressure and heat and the like from the outside, so as to form the long plate-shaped magnet. This results in high manufacturing costs required for forming the long plate-shaped magnet.
However, when the magnet pieces are separately inserted into the magnet insertion hole in the rotor core in order to reduce the costs required for forming the long plate-shaped magnet, the magnet pieces get easily stuck in the middle of the magnet insertion hole and do not reach the bottom of the insertion hole, in the case where corners of the magnet pieces are not subjected to chamfering. On the other hand, when the corners of all the magnet pieces to be inserted are subjected to the chamfering, cost of the chamfering increases greatly, and performance of the magnet deteriorates due to a reduction in magnet volume by the chamfering.